You might be right, I just took a quick look on Ebay and found some interesting stuff.
I'll have to do a serious search this evening.. :)

This seems like something to try. I can't see how it has such a large voltage range..
White 8-LED Super Bright Car Light Bulb 3 Watt DC 8-30V - eBay (item 190459203966 end time Nov-20-10 07:52:49 PST)

Wow, a 10w LED for $7
http://imgs.inkfrog.com/pix/dxy_dxy/DSC00499_.jpg
10W 600LM Warm White Led High Power Lamp 10~12V F - eBay (item 170552346374 end time Nov-12-10 10:55:00 PST)

Or, a more finished look, 9W lamp for $6.39 ??
MR16 48 3528 SMD LED Bulb Lamp Light Warm White 12V 9W - eBay (item 230539862309 end time Nov-17-10 02:28:16 PST)

http://www.eshop111.com/ebay/xpicsc/tbv50bc.jpg

I kinda like the finished look.. :)

I wonder if one of these would make a good headboard reading lamp?

Anyways, perhaps 2 or 3 of these around the house as back-up lighting
or, maybe just standard evening back-ground lighting..?.

One or two of these shouldn't load down a LA battery too much..

Any comments on the specs?

It looks like these have a regulator and will work on battery power directly.

I would say that the stars that I have been experimenting with are old technology now, because these products are much higher wattage and much cheaper.

With those prices, LEDs will take over lighting from other bulb types soon.

I really like the 9W lamp for $6.39, but I know it's for indoor use, not for cars..
I don't think they have a regulator, and that makes me wonder how these would do when used with 13.8vdc??

With the SMD LEDs arrayed on the top like that, I wonder if these are less of a spot light
and more defuse / have a wider beam..?.

Power: approx. 9W
Diameter: 50mm
Height: 38mm
Luminous flux value: 200LM

That's only 22lm/W, a clear failure, close to the efficiency of an incandescent.

The 10W diode emits 600lm, or 60lm/W, which falls just short of a 63lm/W CFL. However, it doesn't include the power supply, and power supplies / voltage regulators on this scale are a big source of inefficiency for LED lamps.

Maybe it's only a 2.5 w lamp??
 

Humm, It sounded too good to be true..

MR16 48 SMD 3528 LED Low Voltage 12 V DC/AC LED Light - Low Voltage LED Lights - LEDLight

"
MR16 48 SMD 3528 LED Light. Very bright over 220 lumens uses only 2.5 watts of power very efficient LED Light. 12 VDC. Approximate size is 1.82in x 1.96in.
"

Hey, they made a movie about it.. :rolleyes:

YouTube - 38976 MR16 48 SMD 3528 LED Low Voltage 12 V DC/AC LED Light




I also found 120vac version that uses 3.5 watts..
48 SMD 3528 LED E27 LED Light Bulb - Household LED Lights - LEDLight

I guess I will start looking for lamp bases with the GX5.3 two prong system, since it seems like that is the preferred choice for building LED bulbs.

My guess as to about 40W incandescent equivalent seems to be about right for the three 1W Star LEDs that I am using. The good thing about the LEDs is that you can focus them easily. 40W focuses down on a workbench to a 3' by 3' area which is bright enough to read and do fine electronics work (look at small parts). This is with 5 degree lenses on the LEDs, although I would probably buy 30d lenses next time.

I think my cost for a three 1W LED system that I then need to put together is about $15, maybe a bit more because I didn't count wire and solder. It would be well worth it to buy premade bulbs with the same output for $20.

I am still waiting on the 3W Stars. I also have some supercapacitors on the way, enough for a 12V system. I'm not sure what I am going to do with them yet, but I will probably experiment and see if they charge up like a battery. Ideally they would be used to hold braking regeneration power on an electric bike but I don't have a functioning ebike at this time. I am thinking to try out a solar powered LED light with no batteries, and see how long the supercaps hold a charge.

I'm going to look more at those little 12v arrays they make to replace lamps in cars.
Those might be more tolerant to my solar chargers..

I'm not up to speed on supercaps, but I know that a 1 Farad capacitor can provide
(or store) 1 amp at 1 volt (1 watt) of power.
So, a 1 Farad flashlight can provide 100 ma @ 1v for 10 seconds.. Or 50ma for 20 sec.. etc.

It sure seems like rechargeable batteries are the best way to go..

Now that's funny.
I am in the same boat. 1 post to go.

I did some testing on Cree 1W Warm White Star LED's to see if they would work within the range of a 12V lead acid battery system, with 4 Star LEDs in series using no voltage regulator.

12V lead acid battery voltage range:

Min: 50% discharge at 67F: 12.61V
12.61V / 4 LEDs = 3.15 V across each LED

Max: Maximum recommended charging rate: 14.4V
14.4V / 4 LEDs = 3.6V across each LED

Note that there may be an inrush current when the LEDs are switched on, this does not take inrush current into account.

Voltage range for each LED: 3.15V - 3.60V

I did some testing using 2 LEDs in series, setting the Voltage using a V regulator, and measuring A. The single LED V is one half of the measured V. Note that amps should be the same for a single LED.

Voltage - single LED V - measured A
7.35V - 3.68V - 0.43A
7.23V - 3.61V - 0.40A
7.21V - 3.60V - 0.38A
7.10V - 3.55V - 0.35A
7.03V - 3.52V - 0.34A
6.84V - 3.42V - 0.30A light still bright
6.71V - 3.36V - 0.26A
6.48V - 3.24V - 0.21A
6.32V - 3.16V - 0.19A
6.24V - 3.12V - 0.17A light still relatively bright
6.04V - 3.02V - 0.12A light still usable though not as bright
5.72V - 2.86V - 0.06A
5.41V - 2.70V - 0.03A
5.18V - 2.59V - 0.01A
4.94V - 2.47V - 0.00A light appears, very dim

At the battery system max, 3.6V across one LED, the measured current is 0.38A, which is higher than specified at 0.35A. Brightness is very bright.

At the battery system min, 3.15V across one LED, the measured current is 0.19A, and brightness is satisfactory.

Ideally, at battery system max (3.6V per LED) current should be the rated current (0.35A), which would indicate a resistance of 3.6V / 0.35A = 10.3 ohms.

A four LED in series system shows 0.38A at 3.6V, or a resistance of 3.6V / 0.38A = 9.5 ohms.

Adding a 1 ohm resistor in series would reduce that amperage at battery system max to just under the rated 0.35A. 3.6V / 10.5 ohms = 0.34A

It might provide some protection against inrush current when switched on.

It would diminish the amperage at the battery system min as follows:
3.15V / 10.5 ohms = 0.30A

At 0.30A the light was still bright.

Each LED needs 1 ohm. With 4 LEDs, 4 ohms are needed.

So with a 12V lead acid battery system, I would recommend using 4 Cree 1W Warm White Star LEDs in series with a 4 ohm resistor, 1W or better, in series. NO REGULATOR IS NEEDED.